It is standard practice to use two weak links in parallel. One has slotted
holes, so there is no strain on it unless the primary weak link fails. If
there is a true overload, both weak links fail. However, if the primary
weak link fails due to fatigue, but the actual forces are below the weak
link limits, the secondary weak link does not fail, preventing an
unnecessary launch failure.

However, if you screw up and use two identical weak links (either both with
regular holes, or both with slotted holes) you have the problem you alluded
to, which is that you effectively have a single weak link with double the
intended strength.

Mike Schumann